A noninvasive measure of respiration can be had from the parameters defining the shape of each breath: inspiratory and expiratory durations, tidal volume ventilation and FRC. The chronological sequences of these variables often display large dynamic oscillations. The aggregation of these rhythms represent the breathing pattern. Our view is that these oscillations reflect the dynamics of respiratory control mechanisms. In exaggerated cases such as Cheyne-Stokes respiration or the apneic spells of infants susceptible to SIDS it is evident that the dynamic aspects of respiratory control are important. We feel that breathing patterns measured under appropriate conditions can be early indicators of deteriorating cardiopulmonary function and hope to establish such a connection. We have developed a computer comb-filter analysis, which displays how the simultaneous strength, frequency and phase of the several oscillations of any subject drift in time. We have seen two categories of oscillations: those whose net effects either tend to reinforce or reduce (compensate) net changes in ventilation. We feel the former oscillation has chemical origins, whereas the latter may be neuromuscularly induced. We plan to investigate the effects of various forms of externally imposed stress upon these rhythmicities, determine the physiological mechanisms responsible for them and consolidate our results into a coherent respiratory control model which incorporates the best current knowledge of system structure and function. Breathing patterns in resting subjects can depend significantly on secondary factors such as the equipment used (e.g., mouthpieces), awareness that breathing is being monitored, posture, nervous agitation due to lack of diversion or sleepiness. We have developed magnetometer apparatus which eliminates the direct effects of standard respiratory monitoring equipment, thus leaving the subject unaware that breathing is under study. We intend to pursue the development of techniques which will, as much as possible, retain subject naivete under the conditions of stress we plan to investigate.